Ask an Immigration Solicitor. Get an Answer ASAP.
Unlikely as I believe she has to apply for her visa from Australia. This can be done I assume by "remote control" i.e. she completes forms here and gets them sent in to Sidney embassy but I believe processing time for granting visa is 21 days (according to UK Border Agency web site)
Look forward to hearing from you, Having spoken to her her current visa expire on the 18th April. This is Tier 5. I have asked UKBA to give priority to our request for COS and am awaiting their response. In the meantime she is hoping there is some way she can stay in the UK whilst visa details are formalised.
Her current visa is Tier 5 under the Youth Mobility Scheme